fix: fix total type in paginate (#228)

<!--
Thank you for your pull request. Please review below requirements.
Bug fixes and new features should include tests and possibly benchmarks.
Contributors guide:
https://github.com/eggjs/egg/blob/master/CONTRIBUTING.md

感谢您贡献代码。请确认下列 checklist 的完成情况。
Bug 修复和新功能必须包含测试，必要时请附上性能测试。
Contributors guide:
https://github.com/eggjs/egg/blob/master/CONTRIBUTING.md
-->

##### Checklist
<!-- Remove items that do not apply. For completed items, change [ ] to
[x]. -->

- [ ] `npm test` passes
- [ ] tests and/or benchmarks are included
- [ ] documentation is changed or added
- [ ] commit message follows commit guidelines

##### Affected core subsystem(s)
<!-- Provide affected core subsystem(s). -->


##### Description of change
<!-- Provide a description of the change below this comment. -->

<!--
- any feature?
- close https://github.com/eggjs/egg/ISSUE_URL
-->

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **Bug Fixes**
- Corrected data type for total count in pagination results to ensure
accurate numeric values.

- **Tests**
- Added a test case to verify accurate total count in pagination
results.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: killagu

core/dal-runtime/src/DataSource.ts

@@ -77,7 +77,7 @@ export class DataSource<T> implements IDataSource<T> {
     ]);
 
     return {
-      total: ret[1],
+      total: Number(ret[1]),
       pageNum: currentPage,
       rows: ret[0].map(t => TableModelInstanceBuilder.buildInstance(this.tableModel, t)),
     };

core/dal-runtime/test/DataSource.test.ts

@@ -146,5 +146,8 @@ describe('test/Datasource.test.ts', () => {
       $id: insertResult.insertId,
     });
     assert.equal(findRow2, null);
+
+    const res = await dataSource.paginate('findByPrimary', {}, 1, 10);
+    assert(res.total === 0);
   });
 });